Looking at api_msg.c line 1254 it check
TCP and only sends as much data as will fit in TCP (648 bytes in
the case above). However after this check at line 1291 it then
does,
if ((conn->write_offset ==
conn->current_msg->msg.w.len) || dontblock)
{
/* return sent length */
conn->current_msg->msg.w.len
= conn->write_offset;
/* everything was written *
write_finished = 1;
conn->write_offset = 0;
}
Since “dontblock” is true in our case it
sets write_finished = 1 which changes the connection state
back to NETCONN_NONE so poll_tcp() will never send the
remaining bytes into TCP……I think this is the problem, but I
don’t understand quite enough to know the proper fix.